Linear cutting staplers are widely used in surgical operations for wound closure, and internal tissue closure and excision. A typical linear cutting stapler as disclosed in U.S. Pat. No. 5,129,570 performs two functions of stapling and cutting, to remove the redundant tissue while stapling the wound. This kind of linear cutting stapler generally includes two jaws (i.e., an upper jaw and a lower jaw), a closing handle for closing the upper jaw and the lower jaw, a staple anvil and a staple cartridge arranged opposite to each other at the front ends of the upper jaw and lower jaw respectively, a firing piece and a cutter which are arranged in the staple cartridge and are moveable synchronously relative to the staple cartridge, and a push button for driving movement of the firing piece and the cutter. Staples are arranged in the staple cartridge. The firing piece pushes a staple pusher successively and pushes the staples towards the staple anvil. The cutter cuts off the tissue between the staple cartridge and the staple anvil.
In clinical application, multiple times of stapling and cutting tissues are often required, and thus the staple cartridge is required to be replaced for many times in an operation. When no staple cartridge is loaded, the push button can be pushed forwards arbitrarily, and then the cutter may be pushed out. This may cause serious consequence as arising from only cutting without stapling. Accordingly, a safety mechanism is provided in the linear cutting staplers in the prior art.
The U.S. Pat. No. 5,129,570 discloses a safety mechanism, in which a safety block with a cutter passage and a staple pushing bar passage is provided in the middle portion of the instrument, and a leaf spring is provided under the cutter. When the instrument is in an opened position, i.e., the upper jaw and the lower jaw are not closed, the leaf spring lifts the cutter upwards, so that the cutter cannot pass through the cutter passage, thereby playing the role of safety. After the staple cartridge is loaded in the instrument, and the two upper and lower jaws are closed, the staple cartridge forces the top portion of the cutter, so that the cutter overcomes the elastic force of the leaf spring and returns to be in alignment with the cutter passage. At this moment, the safety mechanism is deactivated and the instrument can eject the cutter.
The U.S. Pat. No. 7,055,730 discloses another safety mechanism, in which a safety block with a cutter pushing bar passage and a staple pushing bar passage is provided in the middle portion of the instrument, with the safety block being rotatable around the instrument under the action of the torsion spring. When the instrument is in an opened position, i.e., the upper jaw and the lower jaw are not closed, the safety block twists such that neither the staple pushing bar nor the cutter pushing bar are allowed to pass through their passages, thereby playing the role of safety. After the staple cartridge is loaded in the instrument, and the upper jaw and the lower jaw are closed, the staple cartridge forces the safety block such that the safety block overcomes the elastic force of the torsion spring and returns into the normal position. That is, the staple pushing bar and the cutter pushing bar align with their own passages on the safety block respectively, so that both the staple pushing bar and the cutter pushing bar are allowed to pass through the safety block. At this moment, the safety mechanism is deactivated and the instrument can eject the cutter.
All of the above structures are complicated, and difficult to be manufactured and assembled, as well as costly.